过渡金属和磷共掺杂多孔碳作为氧气还原电催化剂

Transition metal and phosphorus co-doped porous carbon as electrocatalyst for oxygen reduction

碳基材料作为非贵金属催化剂具有导电性能高、稳定性能好、价格低廉、环境友好等优点,在燃料电池阴极催化剂领域中引起了广泛的关注,尤其是过渡金属和异原子共掺杂能够显著提高碳材料的氧气还原催化活性。本文采用聚醚(F127)作为软模版,苯酚、甲醛作为碳源,四苯基溴化膦作为磷源,硝酸盐作为过渡金属来源,通过挥发溶剂自组装及高温煅烧过程制备了过渡金属(Co、Fe、Ni、Mn)和磷(P)共掺杂多孔碳材料(TM-P-C)。通过旋转环盘电极研究了TM-P-C在0.1 mol/L KOH电解液中的氧气还原电催化性能。研究结果表明:TM-P-C催化剂具有较高的氧化还原反应(ORR)电催化性能,其ORR活性为P-Co-C>P-NiC>P-Fe-C>P-Mn-C,其中P-Co-C的ORR电催化性能可与商业20wt%Pt/C催化剂相媲美,其电流密度与20wt%Pt/C催化剂的电流密度相当,与20wt%Pt/C仅存在66 mV的半波电位差,表现为ORR的4e–转移途径。制备的TM-P-C催化剂所具有的较高氧气还原电催化活性主要来自于过渡金属和P原子之间的协同作用。此外,TM-P-C催化剂表现出优异的长期稳定性和抗甲醇毒化性能,优于商业化20wt%Pt/C催化剂。

Carbon-based materials,as non-noble catalysts,have attracted extensive attention in the field of cathode catalysts for fuel cells due to their high conductivity,long-term stability,low-cost and environmental friendliness.Especially,the oxygen reduction reaction(ORR)activity of carbon materials can be significantly improved after co-doping with transition metal and heteroatoms.In this work,transition metal(Co,Fe,Ni,Mn)and phosphorus(P)co-doped porous carbon(TM-P-C)was prepared via self-assembly method combined with a carbonization process,in which polyether(F127)was introduced as soft template,phenol and formaldehyde as carbon precursor,tetraphenylphosphine bromide as phosphorus source,and nitrate as transition metal source.The electrocatalytic activity of TM-P-C for ORR in alkaline electrolyte was studied by using the rotating ring-disk electrode(RRDE)technique.The results reveal that TM-P-C exhibits high electrocatalytic performance for ORR in 0.1 mol/L KOH,and the activity follows P-Co-C>P-Ni-C>P-Fe-C>P-Mn-C.Moreover,the ORR performance of P-Co-C is compared to that of commercial 20wt%Pt/C catalyst.The diffusion limiting current density of P-Co-C reaches that of 20wt%Pt/C and a negative shift of about 66 mV exists in the half-wave potential of P-Co-C as compared to 20wt%Pt/C,indicating the four-electron pathway during the ORR.The enhancement in the activity for ORR is mainly attributed to the synergistic effect of P and transition metal doping in carbon of TM-P-C.Moreover,TM-PC shows excellent long-term stability and methanol toxicity resistance,superior to that of commercial 20wt%Pt/C.